<![CDATA[SSH error "can't agree on KEX algorithms"]]>Hello

Has anyone experienced following issue: I have set NetXms to poll Mikrotik router via ssh and each time when attempt is made, router generates error "can't agree on KEX algorithms". When i log in manualy via ssh, then no error. Seems like it started with NetXms version 3.5.90. It used to work on older version and polling script hasent changed.

Egert

]]>https://forum.netxms.org/topic/6711/ssh-error-can-t-agree-on-kex-algorithmsRSS for NodeFri, 13 Nov 2026 18:51:20 GMTMon, 05 Oct 2020 06:00:41 GMT60<![CDATA[Reply to SSH error "can't agree on KEX algorithms" on Thu, 15 Oct 2020 09:19:28 GMT]]>Got it working:

File: nxagentd-ssh-config.conf

HostKeyAlgorithms ssh-dss
KexAlgorithms diffie-hellman-group1-sha1
]]>https://forum.netxms.org/post/28707https://forum.netxms.org/post/28707Thu, 15 Oct 2020 09:19:28 GMT<![CDATA[Reply to SSH error "can't agree on KEX algorithms" on Fri, 09 Oct 2020 05:25:44 GMT]]>Any other ideas ? 🙂 Would be quite bad if Netxms support for Mikrotik ssh is broken.

]]>https://forum.netxms.org/post/28680https://forum.netxms.org/post/28680Fri, 09 Oct 2020 05:25:44 GMT<![CDATA[Reply to SSH error "can't agree on KEX algorithms" on Mon, 05 Oct 2020 11:17:13 GMT]]>Still no go.

Did the following:

nxagentd.conf

[SSH]
ConfigFile = D:\NetXMS\etc\nxagentd-ssh-config.conf

nxagentd-ssh-config.conf

HostKeyAlgorithms +ssh-rsa

restarted agent. In router ssh debug CL line doesent include ssh-rsa

]]>https://forum.netxms.org/post/28669https://forum.netxms.org/post/28669Mon, 05 Oct 2020 11:17:13 GMT<![CDATA[Reply to SSH error "can't agree on KEX algorithms" on Mon, 05 Oct 2020 10:56:17 GMT]]>In agent config you should specify path to SSH config - you cannot just put SSH configuration options to NetXMS agent config. So in nxagentd.conf you should have something like

[SSH]
ConfigFile = /etc/nxagentd-ssh-config

and in file /etc/nxagentd-ssh-config

HostKeyAlgorithms +ssh-rsa

Best regards,
Victor

]]>https://forum.netxms.org/post/28668https://forum.netxms.org/post/28668Mon, 05 Oct 2020 10:56:17 GMT<![CDATA[Reply to SSH error "can't agree on KEX algorithms" on Mon, 05 Oct 2020 10:45:44 GMT]]>Seems like its not working when i change agent conf to include

[SSH]
HostKeyAlgorithms +ssh-rsa

and restart agent. "cl" line didnt change in debug.

]]>https://forum.netxms.org/post/28667https://forum.netxms.org/post/28667Mon, 05 Oct 2020 10:45:44 GMT<![CDATA[Reply to SSH error "can't agree on KEX algorithms" on Mon, 05 Oct 2020 09:54:52 GMT]]>Looks like router supports only ssh-dss and ssh-rsa as host key algorithms and they are not offered by client. You may try to add

HostKeyAlgorithms +ssh-rsa

to your .ssh/config file, or create separate config file for SSH subagent with that line and specify it in nxagentd.conf by adding

ConfigFile = path_to_config

in section [SSH].

Best regards,
Victor

]]>https://forum.netxms.org/post/28666https://forum.netxms.org/post/28666Mon, 05 Oct 2020 09:54:52 GMT<![CDATA[Reply to SSH error "can't agree on KEX algorithms" on Mon, 05 Oct 2020 09:39:52 GMT]]>ssh debug from router: https://ibb.co/pwxSv02

]]>https://forum.netxms.org/post/28665https://forum.netxms.org/post/28665Mon, 05 Oct 2020 09:39:52 GMT<![CDATA[Reply to SSH error "can't agree on KEX algorithms" on Mon, 05 Oct 2020 09:36:30 GMT]]>Hi,

in 3.4 we have added reading SSH config by SSH subagent - could it be that you have something configured there? Also, what KEX algorithms this Mikrotik supports? You can run ssh with -v option and check it. This is sample output from my router:

debug1: SSH2_MSG_KEXINIT sent
debug1: SSH2_MSG_KEXINIT received
debug1: kex: algorithm: diffie-hellman-group-exchange-sha256

Best regards,
Victor

]]>https://forum.netxms.org/post/28664https://forum.netxms.org/post/28664Mon, 05 Oct 2020 09:36:30 GMT<![CDATA[Reply to SSH error "can't agree on KEX algorithms" on Mon, 05 Oct 2020 08:47:08 GMT]]>So when router generates this error the connection does not happen and data is not collected?

]]>https://forum.netxms.org/post/28663https://forum.netxms.org/post/28663Mon, 05 Oct 2020 08:47:08 GMT